[jonascord]

That was the problem with Democrat generals, back then, and McClellean in particular. He figured he'd done his job, since Lee went back across the Potomac. 10 months later, when Meade did the same thing after Gettysburg, letting Lee retreat back into Virginia, Lincoln all but fired him.

Something to consider: Franklin was in command of the Federal reserve corps. McClellan was debating whether to send Franklin in, to press Lee, who was out of fresh troops, and whose army was literally shredded by defending against three massive attacks, and had the river at his back.

Then, Franklin said, "Sir, I'm your only reserve, between Lee and Philadelphia..." and McClellan froze, and canceled the movement... What if?

[Sherman Logan]

Another relevant, “What if?”

Imagine Grant leading the Union army. You simply cannot imagine him not throwing in those last reserves. Which almost certainly would have destroyed the Confederate army.

Whether this would have “ended the war” is something that can never be known, but it seems unlikely the war would have gone on as long as it did.